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ENVIRONM L EALTH DEPARTMENT <br /> SAN JOAQUIN COUNTY <br /> Unit Su ervisorS <br /> Donna K.Heran,R.E.H.S. P <br /> Director 304 East Weber Avenue, Third Floor Carl Borgrnan,R.E.H.S. <br /> A]Olsen,R.E.H.S. Stockton, California 95202-2708 Mike Huggins,R.E.H.S.,R.D.I. <br /> • .. P • Program Manager Douglas W.Wilson,R.E.H.S. <br /> Qil .Ra� Telephone: (209) 468-3420 Margaret Lagorio,R.E_H.S. <br /> Laurie A.Cotuila,R.E.H.S. <br /> Program Manager Fax: (209) 464-0138 Robert McClellon,R.E.H.S. <br /> Mark Barcellos, E.H.S. <br /> JUL 2 6 20 <br /> DICK LELAND <br /> R & L BUSINESS MANAGEMENT (FORMERLY STOCKTON PLATING) <br /> 3826 GLENEAGLES DRIVE <br /> STOCKTON CA 95219-1832 <br /> RE: Stockton Plating SITE CODE: 1986 <br /> 632 S.El Dorado Street <br /> Stockton,CA 95203-3407 <br /> San Joaquin County Environmental Health Department(EHD)is the lead agency providing the <br /> oversight of the investigation and cleanup of releases from underground storage tanks (USTs) <br /> within San Joaquin County. EHD has a contract with California State Water Resources Control <br /> Board to conduct an underground storage tank program. The above referenced site was placed <br /> in the EHD Local Oversight Program (LOP) in April 1991. <br /> EHD has reviewed the Final Remediation Plan prepared by Advanced GeoEnvironmental (AGE) <br /> dated April 23, 2002 and has the following comments. <br /> Two USTs were removed from the above referenced site: one 1,000-gallon leaded gasoline UST <br /> in 1986 and one 2,000-gallon unleaded gasoline UST in 1990. The soil results from the 1990 <br /> UST removal evidenced high concentrations of gasoline from an unauthorized release and <br /> additional assessment and remediation were required. <br /> To date, several soil borings, eight groundwater monitoring wells (MWs), four vapor extraction <br /> wells (VWs), and two groundwater extraction wells (EWs)have been installed. Numerous soil <br /> probe borings were completed to collected soil vapor samples for analyses.The MWs and <br /> borings have defined the vertical and lateral extent of soil and groundwater contamination. <br /> In 1995, a soil vapor extraction test was completed using the 4 VWs. The vertical extent of <br /> contamination in the source had not been defined during the early 1990s, but has since been <br /> delineated with the installation of MW-6 in November 1998. At that time static water was 40 feet <br /> below ground surface (bgs). The static water level at this site was as deep as 45 feet bgs in the <br /> early 1990s when the initial vapor extraction tests were performed, but has risen to 25 feet bgs. <br /> Due to the rise in groundwater, AGE believes that the sustained increase of groundwater <br /> elevation has significantly decreased the potential effectiveness of air sparging in conjunction with <br /> soil vapor extraction as a stand alone treatment method. <br /> In 2001, AGE conducted a groundwater extraction pilot test using two EWs. AGE prepared a <br /> Groundwater Extraction Pilot Test Report dated January 31, 2002. The report stated that this <br /> method is feasible for corrective action. The constant pump rate of 5 gallons per minute was <br /> interpreted as being adequate to control further migration of contaminants downgradient from the <br /> source. <br />